I am using the following but it returns two pieces of data to the server when the second radio button is selected. This is causing the gateway to reject my form.

HTML Code:
 <input type="radio" name="installments" checked value="99"> Continuous Billing
 <input type="radio" name="installments">  limited number of payments - 
  <input type="text" name="installments" value="" maxlength="4" size="4">
This returns - Installments '99' (which is fine) or
Installments 'on' & Installments 'number' (which is not fine).
I can only have one return for the var 'installments' either 99 or the number they select.

I think maybe some JavaScript to check if the second radio button is selected and if so disable it so it won't send any value, or something.... I really don't know much javascript.

Is there a way to do this?